The permanent electric dipole moment of gold chloride, AuCl

Ruohan Zhang, Timothy Steimle, Lan Cheng, John F. Stanton

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Abstract

The [19.20]0<sup>+</sup>-X<sup>1</sup>Σ<sup>+</sup> (0,0) band system of gold chloride, AuCl, has been studied using optical Stark spectroscopy. The [19.20]0 state is analysed as a <sup>3</sup> electronic state, and the observed Stark shifts analysed to determine ground and excited electronic state permanent electric dipole moments, el. A considerably smaller <inf>el</inf> of 0.32 ± 0.17 D for the [19.20]0<sup>+</sup> (v = 0) state, in comparison to that of 3.69 ± 0.02D for the X<sup>1</sup>Σ<sup>+</sup> (v = 0) state is observed. The experimental assignment of the [19.20]0<sup>+</sup> state to a component of the <sup>3</sup>Π state has been corroborated by high-level quantum-chemical calculations using exact two-component theory for treating relativistic effects and the equation-of-motion coupled-cluster approach for describing the electronic excited state. A close inspection of the electronic wave functions for the <sup>3</sup>Π states of gold monohalides reveals significant participation of excitations from the halogen valence p orbitals to the anti-bonding molecular orbitals mainly localised on the gold atom. This leads to a charge transfer from halogen to gold and is responsible for the dramatic reduction of dipole moment in the <sup>3</sup>Π states in comparison to the ground states as observed in the Stark-shift analysis. It has been further demonstrated that this ligand to metal charge transfer increases along the F to I series and leads to predicted dipole moments in the <sup>3</sup>Π states of AuBr and AuI that point towards the gold atoms, qualitatively different than might be anticipated.

Original languageEnglish (US)
Pages (from-to)2073-2080
Number of pages8
JournalMolecular Physics
Volume113
Issue number15-16
DOIs
StatePublished - Aug 18 2015

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Keywords

  • equation-of-motion coupled-cluster
  • gold chloride
  • optical Stark spectroscopy
  • permanent electric dipole moments
  • quantum-chemical calculations

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Condensed Matter Physics
  • Biophysics
  • Molecular Biology

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